Temperature responsive magnetic switch



July 19, 1966 R. s. GAUGLER 3,261,945

TEMPERATURE RESPONSIVE MAGNETIC SWITCH Filed June 29, 1964 1 2Sheets-Sheet 1 Fig. 4

INVENTOR. Richard 8. Gaug/er BY [6M 15 Aflorne y July 19, 1966 R. s.GAUGLER TEMPERATURE RESPONSIVE MAGNETIC SWITCH 2 Sheets-Sheet 2 FiledJune 29, 1964 Sw 5E Q N QQmE Temperature ("F I Fig. 6

RE 09 0 W0 W a 5 0 d w r I 0 C .I .h A w AN/.5 R M Y B United StatesPatent 3 261 945 TEMPERATURE nnsroNsivn MAGNETIC SWITCH Richard S.Gaugler, Dayton, Ohio, assignor to General Motors Corporation, Detroit,Mich, a corporation of Delaware Filed June 29, 1964, Ser. No. 378,832 12Claims. (Cl. Zoo-88) This invention relates to thermostatic switches andmore particularly to magnetically operated thermally responsiveswitching devices.

In many control systems it is desirable to utilize thermostatic switchesthat are responsive to a predetermined sensed temperature to effect adesired controlling action in electrical control circuits.

Typically, to assure switching at an exact temperature control pointcomplex, expensive calibrating means must be included in such devices.The provision of such means, however, reduces the reliability of theswitching device.

An object of the present invention, therefore, is to improve temperatureresponsive magnetically operated switching devices having plural switchpole pieces by the provision therein of a selectively magnetizableswitching element characterized by having little or no magneticcharacteristics below a predetermined temperature and a strong magneticcharacteristic above the predetermined temperature, arranged withrespect to permanent magnet means to produce a reversal of relativemagnetic flux concentrations between the pole pieces for effecting acontinuously reliable switching action.

A further object of the present invention is to reduce the exteriordimensions of temperature responsive magnetically operated switchingdevices having plural switch pole piecesby the provision therein ofpermanent magnet and selectively magnetizable switching elementsarranged in a compact, modular fashion and operable to produce a desiredreversal of relative fiux concentration between switch pole pieces uponsensing a predetermined control temperature.

A still furtherobject of the present invention is to further reduce thecomplexity of such temperature responsive magnetically operated switchesby the provision of electrical terminals on the switch pole piecesadapted to be connected in control circuit means and electricallyconnectable one to the other by conductor means including anarmaturemova-ble relative .to the pole pieces upon flux reversaltherebetween.

Further objects and advantages of the present invention will be apparentfrom the following description, reference being had to the accompanyingdrawings wherein preferred embodiments of the present invention areclearly shown.

In the drawings:

FIGURE 1 is a view in perspective of one embodiment of the temperatureresponsive magnetically operated switch incorporating the presentinvention;

FIGURE 2 is a view in vertical section taken along the line 2-2 ofFIGURE 1;

FIGURE 3 is an enlarged fragmentary sectional view of the area 3 inFIGURE 2;

FIGURE 4 is a view vertical section of another embodiment of theinvention;

FIGURE 5 is a view in vertical section of still another embodiment ofthe invention; and

FIGURE 6 is a chart showing the saturation magnetization curves of amaterial having magnetic characteristics suited for use in the presentinvention.

Referring now to the drawings in FIGURE 1 a switching device 10 isillustrated including a base 12 of a permanent magnetic material havingpoles therein as illustrated in FIGURE 2 which are merely representativeof one suitable. magnet arrangement suitable for use in 3,261,945Patented July 19, 1966 the present invention. The base 12 supports aplurality of soft iron pole pieces 14, 16 and 18 that extend outwardlysothat the pole pieces 14, 16 serve as the side walls of the switchingdevice 10 and the pole piece 18 is located therebetween in spacedparallelism therewith. Terminal extensions 20, 22 present on pole pieces14, 16, respectively, as best illustrated in FIGURE 1, are adapted to beelectrically connected to first and second external circuits each ofwhich is completed by a terminal 24 secured to the magnetic base 12 bymeans of a screw element 26 directed therethrough into electricalengagement with pole piece 18 at the base supported end thereof. Thepole piece 18 has an extension 28 on its free end directed through anopening 39 in an armature 32 whereby shoulders 33 on either side of theextension 28 serve to pivotally support armature 32 with respect to thefree end of the pole piece 14 and the free end of a pole piece 34 formedas a flat plate that is located between and in spaced parallelism withthe pole piece 16 and pole piece 18. Each of the pole pieces 14, 34 hasa surface 36 on the free end thereof that is inclined from a horizontalplane, as best seen in FIGURE 3, so that the surface of the armature 32that mates with the ends of the pole pieces 14, 34 will only contact thepole piece through a limited area to prevent magnetic locking betweenthe armature 32 and its respective mating pole piece.

In accordance with certain principles of .the present invention a firstmagnetizable switching element 38 is located between the pole piece 14and pole piece 18 so that one face thereof is in juxtaposition with themating surface of the pole piece 18 and the other face thereof is inclosely adjacent juxtaposition with but insulated from the inner surfaceof the pole piece 14 by an electrical insulating layer of material 40,for example Mylar, of approximately 2 mils thickness. The layer 40 alsoextends between pole piece 14 and permanent magnet 12 and a likeinsulating layer 41 separates pole piece 16 from magnet 12.

Interposed between the pole pieces 34, 18 is a spacer element 42 formedas a flat plate having opposite flat faces thereon in juxtaposition withthe respective mating surfaces of pole pieces 34, 18. The element 42 ismade of a suitable electrical insulating material, for example nylon.Between the pole pieces 16, 34 is located a selectively magnetizableswitching element 44 like element 38 which has the inner and outer sidefaces thereof located in juxtaposition with coextensive mating surfaceson the pole pieces 34, 16, respectively.

In the illustrated arrangement the pole piece-s, the magnetizableswitching elements and the insulating layers are interconnected by anelongated screw element 46 that is directed therethrough into threadedengagement with nut 47 to maintain such inter-connected elements in acolinear relationship whereby the switching unit has unusually compactouter dimensional characteristics. The screw element 46, in theembodiment illustrated in FIGURES l3, is surrounded by a sleeve 48formed of a suitable electrical insulating material such as nylonwhereby electrical circuits through the various pole pieces arecompletely isolated one from another.

In accordance with certain principles of the present invention, themangetizable elements 38, 44 are constructed of a chromium modifiedmanganese antimonide which have a magnetic characteristic as best shownin FIGURE 6 wherein curves 50, 52 represent the magnetization at varioustemperatures of modified manganese antimonide materials having differentpercentages of chromium therein. The general formula for such materialis Mn Cr Sb with x being the percent of chromium present in thematerial. In such material by varying the chrome content therein afamily of curves like curves 50, 52 are available so that theselectively magnetizable switching elements like 38, 44 can make atransition from a substantial non-magnetic state to a highly magnetizedstate when a predetermined temperature is attained. For example, with amaterial having characteristics as shown in curve 50 when thetemperature reaches F. the magnetic switching element will change from avery low magnetization order to a relatively high magnetization :asillustrated. Accordingly, if the switching arrangement shown in FIGURESl and 2 includes material characterized by the magnetization curve shownat 58 in FIGURE 6 the switch can be located within the cold compartmentof a refrigerating device or the like to respond to the temperaturetherein to perform a warning function by selectively opening and closingthe external circuits from the switch as follows.

When the material is below the predetermined temperature of 15 F. theswitching elements 38, 44 are unmagnetized so that a first magneticcircuit is produced from the base 12 through the pole pieces 14, 18characterized by a relatively strong concentration of magnetic flux inthe vicinity of the end of the pole piece 14 that attracts the armature32 into the position shown in FIGURES l and 2. In this position anexternal electrical circuit 53 including terminals 20, 24 is closedwhereby current passes from a suitable power source 54 through anindicating light 56 or the like in the circuit and thence through theterminal 24, the base 12 that serves as a conductor, screw 26 to polepiece 18, the armature 32 and thence through the pole piece 14 and theterminal to the external circuit. The indicator light 54, for example,can establish that the temperature from the armature 32 so there is arelatively low magnetic flux concentration at the terminal end of thepole piece 14. Simultaneously, the switching element 44 acts to completea serial magnetic circuit from the magnetic base 12 through pole piece16 to the pole piece 34 whereby a relatively large flux concentration isproduced at the terminal end thereof being of a greater magnitude thanthat flux concentration at the terminal end of pole piece 14 whereby thearmature is pivoted about the pole piece 18 to open the external circuit53 and close an external circuit 58 to energize an indicator bulb 60therein that will show that the temperature of the associated coldcompartment is in excess of the desired operating range.

While the switching arrangement is shown associated with a plurality ofexternal circuits having energizable indicia means therein, it will beappreciated by those skilled in the art that the switch is equallysuited for association with circuits for energization of air motorcompressor units, or other electrically energizable operating devicesthat are desirably controlled in response to the predetermined sensedtemperatures.

With reference to FIGURE 4 another embodiment of the invention isillustrated that includes end members 64, 66 serving as pole pieces thatinclude electrical terminals therein like terminals 20, 22 in theembodiment of FIG- URES l-3. The end pole piece 66 has a U-shaped extension 69 therein that joins to a pole piece 68 located intermediate ofand in spaced parallelism to the end pole piece 64 and a pole piece 70interposed in spaced parallelism between pole pieces 66, 68. In thisembodiment of the invention a variably magnetizable switching element 72is located between pole pieces 64 and 68 and arranged in juxtapositiontherewith. A permanent magnet switching element 74 is located betweenpole pieces Y68 and 70 and arranged in juxtaposition relationshiptherewith and a spacer element 76 of a suitable insulating material, forexample nylon, is located between pole pieces 66, 70 in juxtapositionrelationship therewith. As in the embodiment of FIGURES l and 2 theswitching elements and spacing element are formed as relatively compactunits that are joined as an integral unit by an elongated screw element78 that is directed therethrough to threadably receive a nut 30 and boththe nut 80 and screw 73 are insulated in the remainder of the switchingunit by a washer 82 and sleeve element 84, respectively, of a suitableinsulating material, for example nylon.

In this arrangement the pole piece 70 has an extension 86 that isdirected through an opening 88 in movable armature 90 whereby thearmature is pivotally supported on shoulders 91 formed on either side ofthe extension 86. In this arrangement the pole piece 70 is alsoelectrically connected to a terminal (not shown) whereby externalcircuits like the external circuits in the embodiment of FIGURES 1 and 2can be opened and closed by movement of the armature 90 into electricalcontact with the pole 66 or the pole 64.

Assuming that the selectively energizable switching element 72 is likethe switch elements 38, 44, in the embodiment of FIGURES 1-3, when theswitching unit senses a temperature above the predetermined switchingtemperature, as for example 15 F., the switching element 72 has a highmagnetization whereby a serial magnetic circuit is completed from thepermanent magnet 74 through switching element 72 and the pole 64 wherebya strong magnet flux concentration is produced at the terminal end ofpole piece 64 to attract the armature thereagainst. Since the magneticpath through the U-shaped pole piece extension 69 and pole piece 66 issubstantially greater than the path through the previously describedserial circuit, the magnetic flux concentration at the terminal end ofthe pole piece 66 is relatively smaller than that at the terminal end 64during this phase of operation.

In this arrangement when the temperature is below the predeterminedswitching temperature the switching element 72 is no longer magnetizedand the magnetic circuit through the pole piece 68 and pole piece 66 isthereby more direct than that across switching element 72 which is noweffectively an air gap. The magnetic flux concentration in the vicinityof the terminal end of pole 66 is thereby stronger than that in thevicinity of the terminal end of pole piece 64 and the armature pivotsabout the end of pole piece 70 to close against pole piece 66 toenergize the other external circuit.

In the embodiment illustrated in FIGURE 5 a switch is shown includingend plates 92, 94 that serve as pole pieces. In this arrangement betweenpole pieces 92, 94 is located a plate 96 that has an extension 98 on theend thereof directed through an opening 100 in an armature 102 that isthereby pivotally supported by the terminal end of plate 96 for movementwith respect to the terminal ends of pole pieces 92, 94 that are alignedlike those in FIGURES 1 and 2 to prevent magnetic locking between thepole pieces and armature. In this embodiment the pole pieces 92, 94 areturned inwardly at ends 104, 106, respectively, and the end of the plate96 is bent at 108 toward pole piece 92. The bent end 106 of the polepiece 94 serves to supportingly receive a permanent magnet switchingmember 110 that is thereby located between pole piece 94 and plate 96 injuxtaposition relationship therewith. Similarly, a second permanentmagnet switching member 112 is supported by the bent end 108 of plate 96and a variably magnetizable switching element 114 is supported by thebent over portion 104 of pole piece 92. The permanent magnetic member112 and the switching element 114 are located in juxtaposition betweenthe plate 96 and pole piece 92.

Above the permanent magnet 110 is located another variably magnetizableswitching element 116 that is between the pole piece 94 and plate 96 injuxtaposition relationship therewith and above the supported members112, 114 is located a block 11 8 of electrical insulating material, forexample nylon, that is in juxtaposition relationship with pole piece 92and plate 96. In this embodiment the various switching members andinsulating blocks are held as an integral modular unit by an elongatedscrew element 120 threadably engaged by nut element 122 for holding theparts together. In this arrangement a first contact 124 is carried onthe end of U-shaped spring member 126 serving as an electrical terminal,that is fixedly secured to the insulating block 118 by a screw member128. The contact 124 is located and arranged to electrically connect ormate with a movable contact 130 carried by a conductor strip 132 securedto a layer of insulating material 134 for electrically insulating thecontact 130 from the armature and pole pieces of this embodiment of theinvention.

In the position shown in FIGURE 5 the variably magnetizable switchingelements 114, 11 6 are highly magnetized to thereby complete a firstserial magnetic circuit from the permanent magnet 112 through the polepiece 92 so as to produce a relatively strong magnetic fluxconcentration on the terminal end of pole 92 and to complete a magneticcircuit from permanent magnet 110 and shunted between pole piece 9 4 andplate 96 whereby the flux concentration at the end of pole piece 94 isrelatively weak compared to that at the end of pole piece 92. In thisposition the contact 130 is moved into electrical contact with thetfixed contact 124 to complete an external indicating, operating or thelike electrical circuit.

When the switching elements 114, 116 sense a temperature below theswitching temperature, they immediately make a sharp transition tolittle or no magnetization whereby the pole piece 92 is etfectivelymagnetically isolated from the permanent magnets and the pole piece 94and an unshunted magnetic circuit is completed from magnet 110 throughpole piece 94 to produce a relatively strong flux concentration at theterminal end thereof which moves the armature into contact therewith tothereby separate contact 132 from contact 124 to open the externalcircuit.

In view of the above description of the various embodiments of thepresent invention, it will be appreciated by those skilled in the artthat the present invention provides a switching device that is unusuallycompact and unusually economical in that the operative parts thereofserve as the switch housing and in some cases as portions of both amagnetic circuit system and an electrical circuit system. These multiplepurpose aspects and the compact nature of the switch is attributed to agreat degree to the use of the variably magnetizable switching elementthat is characterized by a very low magnetization on one side of thecontrol temperature and a very high magnetization on the other side ofthe control temperature. Moreover, by using such a material, a highlyresponsive switching device is provided that is suitable for operatingan electrical device that requires a very reliable switching device inassociation therewith to carry out its intended operation over asubstantial period of time.

While the embodiments of the present invention as herein disclosedconstitute preferred forms, it is to be understood that other formsmight be adopted.

What is claimed is as follows:

1. In a temperature responsive switch the combination of, a first pairof pole pieces and a second pair of pole pieces, a selectively magnetizable switching element arranged between at least one pair of said polepieces, permanent magnet means associated with said magnetizableswitching element and coa cting therewith to produce a firstpredetermined differential flux pattern in said first and second pair ofpole pieces, movable armature means responsive to said predetermineddifierent-ial flux pattern to be drawn toward one of said pair of polepieces, said switching element having a low magnetization below apredetermined temperature and a high magnetization immediately above thecritical temperature, said switching element upon sensing the criticaltemperature producing a reversal in said first predetermined fluxpattern to cause said movable armature means to be attracted to theother of said pair of pole pieces.

2. A temperature responsive magnetically operated switch comprising apermanent magnet, a first and a second pole piece, a variablyma-gnetizable switching element interposed between said permanent magnetand at least one of said pole pieces, said permanent magnet and saidvariably magnetizable switching element producing a first predetermineddifferential magnetization between said pole pieces, said switchingelement upon sensing a predetermined temperature immediately shunting aportion of the :fiux pattern from said permanent magnet to produce areversal of the relative strength of the flux concentration in saidfirst and second pole pieces, an armature, means for pivotallysupporting said armature with respect to said pole pieces whereby theposition thereof upon reversal of the relative flux concentrationstrength therein is reversed.

3. In a temperature responsive magnetically operated switch, thecombination of, a pair of pole pieces, a permanent magnet means forproducing a predetermined flux pattern in said pole pieces, a variablymagnetizable switching element, means for interconnecting said polepieces, magnet and switching element into a unitary structure whereinsaid pole pieces, magnet and switching element are aligned colinearly asa modular unit, said variably magnetizable switching element having arelatively low magnetization below a predetermined temperature and arelatively high magnetization above the predetermined temperature, saidswitching element being operative to effect a reversal of the relativeflux concentrat-ion produced in said pole pieces by said permanentmagnet means upon sensing of the predetermined temperature.

4. In a temperature responsive magnetically operated electrical switchthe combination of a permanent magnet, a variably rnagnetizableswitching element having substantially no magnetization below apredetermined temperature and a substantial magnetization above thepredetermined temperature, a first and a second pole piece ofelectrically conductive material, a conductor element located betweensaid first and second pole pieces, means including a movable armaturefor electrically connecting said first and second pole pieces inexternal circuits through said conductor element, said permanent magnetproducing a predetermined flux pattern in said first and second polepieces, said flux pattern being varied by said switching element uponits sensing a predetermined control temperature, said variation in fluxpattern acting upon said armature means to produce movement thereofagainst one or the other of said first and second pole pieces tocomplete the electrical circuits associated therewith.

5. In a temperature responsive magnetically operated switching device,the combination of a first and second conductor element, a thirdconductor, a permanent magnet, a variable magnetizable switchingelement, said permanent magnet and switching element producing a firstpredetermined flux pattern in said conductors below a predeterminedtemperature and a second flux pattern therein immediately at thepredetermined temperature, armature means movable by the variation influx patterns to electrically connect one of said first and secondconductors to said third conductor during one of the changes in fluxpattern whereby said first and second electrical conductors are includedas a part of an external electrical circuit controlled by said switchingdevice.

6. In a temperature responsive magnetically operated switch, thecombination of a switch housing including end walls serving ascombination electrical terminals and magnetic pole pieces, a permanentmagnet, a variably magnetizable switching means, means for fasteningsaid magnet and said switching means between said end walls in supportedrelationship thereon, said permanent magnet producing a predeterminedflux pattern in said end walls, said switching means operative to eflecta reversal of relative flux concentration strength in said end walls ata predetermined critical temperature, an armature, said armature beingmovable upon the reversal of flux concentration between first and secondswitching controlling positions.

'7. In the combination of claim 6, said permanent magnet serving as abase for supportingly receiving said combination electrical terminal,pole piece end wall portions.

3. In the combination of claim 6, means for pivotally supporting saidarmature with respect to said first and second end walls forsup-portingly directing said armature into first and second posit-ionsupon flux reversal.

9. In the combination of claim 6, a third pole piece located betweensaid end walls, said switching means including a variably magnetizrableelement located between one of said end walls and said third pole piecefor selectively varying the flux concentration in said third pole pieceupon sensing the critical temperature, said third pole piece serving toattract said armature upon a first flux reversal and said other of saidend walls serving to attract said armature upon a second reversal.

10. In a magnetically switching device the combination of a pair ofspaced end walls serving as a portion of a switch housing and as anelectrical terminal and a magnetic pole piece, a third pole piece, amagnetic member connecting said third pole piece to one of said endwalls, an armature, a member for pivotally supporting said armatureserving as an electrical conductor, a permanent magnet disposed betweensaid third pole piece and said conductor member, a variably magnetizableswitching element disposed between one of said end walls and said thirdpole piece, said switching element having a low magnetization below apredetermined temperature and a high magnetization above thetemperature, said switching element upon sensing the predeterminedtemperature increasing the flux concentration in said one of said endwalls in excess of the flux concentration in the other of said end wallsto attract said armature thereaga-inst to complete an externalelectrical circuit including said one end wall, said armature and saidelectrical conductor member, said switching element reversing the fluxpattern between the end walls below the predetermined temperature toincrease the flux concentration at the other end wall above that at saidone end Wall whereby the armature is attracted to said other end walland separated from said one end wall to open the first electricalcircuit and complete another electrical circuit including the other endwall, the armature and the electrical conductor member.

11. In the combination of claim 10, said pole pieces, electricalconductor member, magnet and switching elements being arrangedcolinearly in a compact manner, and means fior interconnecting saidcolinearly arranged parts.

12. In a temperature responsive magnetically operated switch thecombination of, a first permanent magnet, a second permanent magnet,first and second variably magnetizable switching elements, a pluralityof support plates of magnetizable material located in spaced parallelismwith one another, one of said permanent magnets and one of saidswitching elements supported in juxtaposition relationship between firstand second of said plates, another of said permanent'magnets and anotherof said switching elements being supportingly received in juxtapositionrelationship between the second and a third of the spaced plates, meansfor integrally connecting said plates, switch-ing elements and permanentmagnets as a compact, modular unit, an armature, said second plateserving to pivotally support said armature for movement with respect tosaid first and third plates, said permanent magnets producing apredetermined relative flux concentration between said first and thirdplates for attracting said armature toward one of said plates, saidswitching elements upon sensing a predetermined temperature having asubstantial magnetization to effect a reversal of flux concentration insaid second and third plates for attracting the armature toward anotherof said first and third plates, and co'acting means on said armature andswitch means operatively connected with said armature for eifecting apredetermined switching action upon such movement of said armature.

References Cited by the Examiner UNITED STATES PATENTS 6/1906 Thomson.

OTHER REFERENCES BERNARD A. GILHEANY, Primary Examiner.

R. N. ENVALL, JR., Assistant Examiner.

1. IN A TEMPERATURE RESPONSIVE SWITCH THE COMBINATION OF, A FIRST PAIROF POLE PIECES AND A SECOND PAIR OF POLE PIECES, A SELECTIVELYMAGNETIZABLE SWITCHING ELEMENT ARRANGED BETWEEN AT LEAST ONE PAIR OFSAID POLE PIECES, PERMANENT MAGNET MEANS ASSOCIATED WITH SAIDMAGNETIZABLE SWITCHING ELEMENT AND COACTING THEREWITH TO PRODUCE A FIRSTPREDETERMINED DIFFERENTIAL FLUX PATTERN IN SAID FIRST AND SECOND PAIR OFPOLE PIECES, MOVABLE ARMATURE MEANS RESPONSIVE TO SAID PREDETERMINEDDIFFERENTIAL FLUX PATTERN TO BE DRAWN TOWARD ONE OF SAID PAIR OF POLEPIECES, SAID SWITCHING ELEMENT HAVING A LOW MAGNETIZATION BELOW APREDETERMINED TEMPERATURE AND A HIGH MAGNETIZATION IMMEDIATELY ABOVE THECRITICAL TEMPERATURE, SAID SWITCHING ELEMENT UPON SENSING THE CRITICALTEMPERATURE PRODUCING A REVERSAL IN SAID FIRST PREDETERMINED FLUXPATTERN TO CAUSE SAID MOVABLE ARMATURE MEANS TO BE ATTRACTED TO THEOTHER OF SAID PAIR OF POLE PIECES.